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CONSERVING CONCRETE HERITAGE
AN EXPERTS MEETING TO IDENTIFY RESEARCH
NEEDS TO ADVANCE THE FIELD
The Getty Conservation Institute
June 9-11, 2014Los Angeles, CA
Luc CourardUniversity of Liège, Belgium
Concrete Surface Engineering for Cultural Heritage
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Situation of our infrastructure today
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Factors contributing to the degradation of
concrete structures (BCA, 1997)
12%
39%
16%
7%
4%
2%
8%
1%13%
low cover
environment
poor quality concrete
poor quality detailing
poor workmanship
wrong specification
failure joint/waterproofing
inadequate conceptual
designwrong material selection
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Factors contributing to the failure of repair
(Tilly, 2004)
33%
18%16%
12%
4%
14%
3%
incorrect design
material
workmanship
diagnosis
weather (during works)
others
unknown
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Concrete churches in Liège county: pathologies
Saint-Hubert
Saint-Francis of Sales
Holy Heart and
Our Lady of
Lourdes
Saint-MartinSaint-Virgin Maria
Saint-Vincent
Saints Peter and Paul
Saint-GeorgesSaint-Juliana
(Churches and concrete in Liège district: history, architecture
and pathologies. A. Gillard, L. Courard and P. Paquet. Restoration
of Buildings and Monuments, 17 (1) (2011) 3–14)
Corrosion
Cracking
Humidity
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Repair: how to select materials?
Condition 1 : spreading / wettability
Condition 2 : physico-chemical interaction
Condition 3 : mechanical interlocking
Principles
(L. Courard, Parametric Study for the Creation of the Interface
between Concrete and Repair Products. Mat. Struct., 33
(January-February 2000), 65-72.)
High wetting propensity
Low wetting propensity
Adhesion
Specific adhesion
Physico-chemicalinteractions
Thermodynamic considerations Chemical bonding
Mechanical interlocking
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Repair: how to selects materials?
Compatibility
repair system
- substrate
deformability
E Modulus creep shrinkagethermal
deformations
permeability chemistryelectro-
chemistryaesthetics
(Repair of concrete industrial floors with bonded cement-based
material overlays: some recommendations L. Courard, A. Vaysburd and
B. Bissonnette. Seventh
International Colloquium Industrial Floors ’10, (Ed. K.
Littmann, Technische Akademie Esslingen), Ostfildern/Stuttgart,
Germany (14-16 December 2010), pp. 617-622)
Concept of compatibility for strong, long-lasting adhesion
� substrate
� repair material
� environment
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Definition
Scientific and technological approaches addressing all
surface-related
considerations, notably those pertaining to adhesion of a
surface treatment
intended to improve the properties of the substrate, such as its
resistance to
corrosion and abrasion, or its aesthetic properties
Concrete Surface Engineering
(Surfology: what does it mean for polymer concrete composites?
L. Courard and A. Garbacz. Restoration of Buildings and Monuments
16 (4/5) 2010, 291-302.)
Surface engineering covers
all phenomena involved in the preparation
of the substrate near-to-surface layer
and adherence of a surface treatment
in given conditions
Example: hydrophobic treatment
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What is surface concrete, of what is it made ?
Concrete Surface Engineering
= ½ d (with d : maximum size of aggregates)
Bulk concreteSkin
21 3 1
2
3
(Influence of the reuse of OSB and marine plywood formworks on
concrete facing color. L Courard, M. Martin, C. Goffinet, N.
Migeotte, J. Piérard and V. Polet.
Materials and structures 45(9), 2012, 1331-1343)
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What is the effect of water at the interface?
Concrete Surface Engineering
γSA
= γSB
+ γAB
. cos θγSV
= γSB
+ γBV
. cos θ
γB
. cos θB
- γA
. cos θA
< γAB
γB
. cos θB
- γA
. cos θA
> γAB
Equilibrium : the difference between tensions
of adhesion is inferior to interfacial tension
No equilibrium : liquid B will expulse liquid A
the liquid with the higher tension of adhesion
will expulse the other one from the surface
γS
= γSA
+ γA
. cos θA
γS
= γSB
+ γB
. cos θB
Saturation level of the superficial zone of concrete and
adhesion of repair systems. L. Courard, J. F. Lenaers, F. Michel
and A. Garbacz. Construction and Building
Materials 25 (5), May 2011, 2488-2494)
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Effect of water at the interface
Concrete Surface Engineering
(Hygro-thermal application conditions and adhesion. L. Courard,
A. Darimont, R. Degeimbre and J. Wiertz. Fifth International
Colloquium Industrial Floors ’03,
(Ed. P. Seidler, Technische Akademie Esslingen),
Ostfildern/Stuttgart, Germany (21-23 January 2003), 137-142)
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What are the effects of surface texture (roughness)?
Devices for the measurement of surface texture
Concrete Surface Engineering
Mechanical profiling
Measured area : 200 x 200 mm2
Stylus shape: truncated cone
Stylus diameter: 1 mm
Measurement pitch: 1 mm
Atos I 3D Digitizer
Fringe patterns
Measured area (range):
120 × 100 – 1000 × 800 mm2Spatial resolution: 0.04 - 1 mm
Ma
the
ma
tica
l
tre
atm
en
t
(Combination of mechanical and optical profilometry techniques
for concrete surface roughness characterization. F. Perez, B.
Bissonnette and L. Courard. Mag.
Concrete Res, 61(6) 2009, 389-400)
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Texture (roughness / waviness)
vs.
Surface preparation technique
Concrete Surface Engineering
(Surface analysis of mineral substrates for repair works:
roughness evaluation by profilometry and surfometry analysis. L.
Courard and M. Nélis. Mag. Concrete Res.,
55(4) (August 2003), 355-366)
scabbling
shotblasting
polishing
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Roughness vs. adhesion
Concrete Surface Engineering
(Concrete removal techniques: influence on residual cracking and
bond strength. B. Bissonnette, L. Courard, A. Vaysburd and N.
Bélair. Concrete International, 28(12) 2006, 49-55)
jack-hammering
no treatment
sandblastingwater jetting
polishing
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Roughness vs. microcracking
NT – no treatment; WJ – water jetting – pressure 124 psi/250MPa;
SB – sandblasting; SCR – scabbling; J+SB –
jack hammering of weight 7,14,21 kg + sandblasting
Concrete Surface Engineering
(Characterization of concrete surface roughness and its relation
to adhesion in repair systems. A. Garbacz, L. Courard and K.
Kostana. Mater. Charact., 56 (2006) 281-289)
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Degradation of historical concrete buildings and monuments
Causes quality of concrete → evaluaIon?
insufficient concrete cover → evaluaIon?
freeze-thaw cycles
Effects corrosion of steel reinforcement by carbonation
disintegration
Needs resistance to carbonation
aesthetics requirements
water repellency
( + compatibility issues)
Concrete Surface Engineering
